Mayor of London Boris Johnson, who two years ago gave chase on his bike to a gang of girls attempting to mug a woman in Camden, has played Good Samaritan again after stopping to help a fellow cyclist who had been knocked off his bike and injured when a minicab driver opened his car door into his path.

The incident took place on Monday evening in Southwark Street as Mr Johnson returned – on a Boris Bike, naturally – to City Hall following a meeting in the West End, reports the London Evening Standard.

Mr Johnson telephoned for an ambulance and remained with the victim until emergency services arrived at the scene, adds the newspaper, which also provided an eyewitness account from project manager Liam Smith, who was passing by.

"I saw Boris speed past me on his Boris bike and go through two red lights,” said Mr Smith, with perhaps a little more detail than the Mayor would appreciate.

“A short while later I saw him at the junction of Southwark Bridge Road with a small crowd of people and an injured cyclist.

"The man was bleeding from his mouth and had cuts on his hands and knees,” Mr Smith added. “He was very pale and barely conscious.

"Boris was on the phone calling an ambulance and then he was saying to the man, 'stay awake, stay awake, what is your name?'

"He was shaking him gently to stop him from passing out. A guy brought him a glass of water and was saying, 'don't worry, you are being looked after by the Mayor of London'. The cyclist said his name was Richard and he was on his way to visit a friend."

Mr Smith added that an off-duty member of St John’s Ambulance helped administer first aid to the stricken cyclist, while the mini cab driver also remained at the scene.

While Mr Johnson is without doubt one of the capital's most high-profile cyclists, and certainly the one best placed to influence policy when it comes to getting around the city on two wheels, some of his decisions have been criticised as being at odds with his much-vaunted desire to bring about a "cycling revolution" in London.

There has been a series of protests by cycle campaigners against his and Transport for London's decision to scrap a temporary 20 mile an hour speed limit on Blackfriars Bridge, while two years ago he was criticised for effectively scrapping the Commercial Vehicle Education unit after axing funding for the body, which was staffed and operated by the Metropolitan Police.

Heading east there is a cycle lane right in the door zone of some parking bays, which isn't great. Although in London plenty of people will swing a car door open fully without looking at whats coming along the road.

The eyewitness statement sounds a bit odd. There is nowhere on Southwark Road where you could see someone jumping two red lights as they are quite far apart.

What a hero. At least he stopped and did something. Good on him. As for voting for him. He's better than the rest but that's not saying much. He can't please everyone and generally I think he gets it right.